Axial piston hydraulic transducer shoe retainer structure

ABSTRACT

In hydraulic transducer apparatus of axial piston type having a rotatable piston barrel mounted within a body, a rocker cam defining a swash plate having a slip surface pivotally mounted within an accommodating cradle including within the said body, and a plurality of piston structures including piston shoes reciprocatively mounted with such piston shoes disposed in abutting relation with the swash plate. A piston shoe retainer structure is provided operable to urge said piston shoes into even and uniform abutting contact with the swash plate slip surface. The shoe retainer structure comprises: A shoe retainer plate is provided which is rotatable with the pistons and which respectively retains the piston shoes against the slip surface. A spherical retainer socket is disposed to urge the plate and the shoes against the swash plate surface through a thrust bearing, the retainer socket having means cooperating with said rocker cam to prevent rotation of the retainer socket. A fastener means extends into the rocker cam and connects the retainer socket and the retainer plate through a spherical washer universally fitted into the socket. Resilient retainer means, such as a Belleville spring structure, connects the fastener means into prestressed relation with the rocker cam. The shoe retainer structure is operable independently of the piston barrel structure.

Raymond et al.

Jan. 8, 1974 AXIAL PISTON HYDRAULIC TRANSDUCER SHOE RETAINER STRUCTURE Inventors: David G. Raymond; Gary C. Smith,

Jr., both of Westerville; Alan H. Viles, Columbus, all of Ohio Assignee: Abex Corporation, New York, NY.

Nov. 16, 1972 [52] US. Cl. 91/488, 91/505 [51] Int. Cl. F0lb 113/04 [58] Field of Search 91/488, 499, 501, 91/504-507 [56] References Cited UNITED STATES PATENTS 2,608,159 8/1952 Born 91/488 3,110,267 11/1963 Vetter 91/485 3,241,495 3/1966 Diedrich et al. 91/507 3,410,220 11/1968 Kratzenberg et a1. 91/499 3,437,015 4/1969 Kubilos; 91/499 1 FOREIGN PATENTS OR APPLICATIONS France 91/501 5 7] ABSTRACT In hydraulic transducer apparatus of axial piston type having a rotatable piston barrel mounted within a body, a rocker cam defining a swash plate having a slip surface pivotally mounted within an accommodating cradle including within the said body, and a plurality of piston structures including piston shoes reciprocatively mounted with such piston shoes disposed in abutting relation with the swash plate. A piston shoe retainer structure is provided operable to urge said piston shoes into even and uniform abutting contact with the swash plate slip surface. The shoe retainer structure comprises: A shoe retainer plate is provided which is rotatable with the pistons and which respectively retains the piston shoes against the slip surface. A spherical retainer socket is disposed to urge the plate and the shoes against the swash plate surface through a thrust bearing, the retainer socket having means cooperating with said rocker cam to prevent rotation of the retainer socket. A fastener means extends into the rocker cam and connects the retainer socket and the retainer plate through a spherical washer universally fitted into the socket. Resilient retainer means, such as a Belleville spring structure, connects the fastener means into prestressed relation with the rocker cam. The shoe retainer structure is operable independently of the piston barrel structure.

7 Claims, 4 Drawing Figures PATENTEUJAH 8 I974 SHEET 1 Bf 2 PATENTEUJAH a 1974 SHEET 2 BF 2 slTesfims AXIAL PISTON HYDRAULIC TRANSDUCER SIIOE RETAINER STRUCTURE BACKGROUND OF THE INVENTION l SUMMARY OF THE INVENTION The invention provides axial piston fluid flow transducer apparatus wherein the components are provided as a composite unit of relatively simple construction for facility of installation and of self-adjustment.

The invention also provides a piston shoe retainer structure which serves to retain the piston shoes against the pump swash plate in an even and uniform manner even though there may be some distortion and/or misalignment within the pump as caused during fabrication or, more importantly, as caused during operation when the pump is operating under stress of high fluid pressures.

The invention further provides a piston shoe retainer structure which is adapted to function independently of the pump piston barrel structure.

The foregoing provisions and other objects and advantages of the invention are attained in hydraulic transducer apparatus ofaxial piston type having rotatable piston barrel means mounted within a body, rocker cam means defining a swash plate having a slip surface pivotally mounted within accommodating cradle means includingwithin the body, and a plurality of piston means including piston shoes reciprocatively mounted with the piston shoes disposed in abutting relation with said swash plate. A piston shoe retainer structure is provided operable to urge the piston shoes into universal abutting contact with said swash plate slip surface which comprises: A shoe retainer plate rotatable with the piston means and respectively retaining the piston shoes against the slip surface. A spherical retainer socket means is disposed to urge the plate and shoes against the surface through thrust bearing means, the retainer socket having means cooperating with the rocker cam to prevent rotation of the retainer socket. A fastener means extends into the rocker cam and connects theretainer socket and the retainer plate through a spherical washer means universally fitted into the socket means. A resilient retainer means connectsthe fastener means into pre-stressed relation with the rocker cam means. The arrangement is-such that the shoe retainer structure is operable independently of the piston barrel means.

BRIEF DESCRIPTION OFTHE DRAWINGS FIG. 3 is a partial axial section of the pumptaken along the line 33 of FIG. 2.

FIG. 4 is an enlarged portion of the structure shown in FIG. 3. Description of the Preferred Embodiment Referring to FIGS. I through 4, there is shown a hydraulic transducer pump or motor 46 of the axial piston type having a drive shaft 11 rotatably mounted through a port block 12 into a rotatable piston barrel 13, which in turn is rotatably mounted within a pump body 14 by means of a bearing assembly 15. A plurality of pump pistons 16 are mounted within respective cylinders 17 defined within the barrel 13. A piston shoe 18 is pivotably attached to each piston and retained against a creep plate 19 by means of a shoe retainer assembly 21. Creep plate 19 is also termed a swash plate herein. Creep plate 19 and retainer assembly 21 are mounted with a rocker cam 22 which is received in pivoted relation within a cradle 23 defined by and within an end cap 24. End cap 24 abuts a spacer ring 25 which supports bearing assembly 15 and barrel 13 into appropriate operating position when end cap 24 is assembled with body 14 as shown. End cap 24 is connected with body 14 by means of fasteners (not shown) such as cap screws.

As seen in FIG. 4, shoe retainer assembly 21 is comprised of a shoe retainer plate 26 which retains piston shoes 18 against creep plate 19 during operation of the pump 46. Retainer plate 26 is supported from rocker cam 22 through the combination of a thrust bearing 27, a spherical hold-down socket 28 abutting the thrust bearing and spherical retainer washer 29 received in the socket 28. A cap screw or bolt 33 extends through and retains washer 29 in a fixed relation relative to rocker cam 22. Lugs 31 project from socket 28 into slots 32 defined in a rocker cam 22 to prevent rotation of shoe retainer assembly 21 relative to rockercam 22.

Cap screw 33 is resiliently secured in rocker cam 22 by means of a castle nut 36 which retains a spring retainer 34. Spring retainer 34 in turn retains spring means 35 (Belleville springs, for example) in compression. A retainer key 37 restrains rotation of nut 36 to an adjusted position which establishes the compressive force exerted by spring means 35. It is to be noted that the shoulder of spring retainer 34 slightly clears the counterbore 43 of the rocker cam 22 to enable retainer plate 26 to move very slightly in response to axial force applied along cap screw 33. The purpose of this feature, as shown and described, is to allow only limited lift off of piston shoes 18. Such lift off behavior is well recognized.

The counterbore 43 opens into a bore 44, forming a socket which houses the elements 33, 34, 35, 36, and 37 of shoe retainer assembly 21.

Further referring to FIG. 4, the inner end of drive shaft 11 is seen to be secured in splined connection within barrel 13 by means of a fastener, such as a cap screw 39, drawn down against a spring means 41 (such as Bellevillesprings) and a support washer 42, th'e. washer 42 being in abuttmen-t with the barrel 13 as shown. The shaft 11 is retained in the opposite direction by thrust means (not shown) provided within port block 12.

The advantages of the shoe retainer assembly 21, as shown, are to provide an'even retaining force on each of the piston shoes 18 to retain the shoes appropriately against swash plate 19 while permitting universal movement between the spherical hold-down socket 228 and spherical retainer washer 29 to accommodate for any distortion or misalignment in the system as may be caused during operation under stress of high fluid pressure. It is to be noted that the shoe retainer 21 is selfcontained with rocker cam 22 and functions completely independently of the assembly of piston barrel 13.

The foreging description and drawings will suggest other embodiments and variations to those skilled in the art, all of which are intended to be included in the spirit of the invention as herein set forth.

That being claimed is:

1. In hydraulic transducer apparatus of axial piston type having rotatable piston barrel means mounted within a body, rocker cam means defining a swash plate having a slip surface pivotally mounted within accommodating cradle means included within said body, and a plurality of piston means including piston shoes reciprocatively mounted with said piston shoes disposed in abutting relation with said swash plate, a piston shoe retainer structure operable to urge said piston shoes into universal abutting contact with said swash plate slip surface comprising: a shoe retainer plate rotatable with said piston means and respectively retaining said piston shoes against said slip surface, a spherical retainer socket means disposed to urge said plate and said shoes against said surface through thrust bearing means, said retainer socket having means cooperating with said rocker cam to prevent rotation of said retainer socket, a fastener means extending into said rocker cam means and connecting said retainer socket means and said retainer plate through a spherical washer means universally fitted into said socket means, and resilient retainer means connecting said fastener means into prestressed relation with said rocker cam means.

2. The transducer apparatus of claim 1 wherein said shoe retainer structure is operable independently of said piston barrel means.

3. The transducer apparatus of claim 1 wherein said fastener means is a threaded bolt extending into said rocker cam and retained by a threaded nut.

4. The transducer apparatus of claim 3 wherein said resilient retainer means comprises Belleville spring means compressed through said threaded nut.

5. The transducer apparatus of claim 1 wherein said fastener means and said resilient retainer means are operable to cause said retainer plate to resiliently retain said piston shoes against said slip surface.

6. The transducer apparatus of claim 4 wherein said fastener means and said resilient retainer means are operable to cause said retainer plate to resiliently retain said piston shoes against said slip surface.

7. The transducer apparatus of claim 6 wherein said shoe retainer structure is operable independently of said piston barrel means. 

1. In hydraulic transducer apparatus of axial piston type having rotatable piston barrel means mounted within a body, rocker cam means defining a swash plate having a slip surface pivotally mounted within accommodating cradle means included within said body, and a plurality of piston means including piston shoes reciprocatively mounted with said piston shoes disposed in abutting relation with said swash plate, a piston shoe retainer structure operable to urge said piston shoes into universal abutting contact with said swash plate slip surface comprising: a shoe retainer plate rotatable with said piston means and respectively retaining said piston shoes against said slip surface, a spherical retainer socket means disposed to urge said plate and said shoes against said surface through thrust bearing means, said retainer socket having means cooperating with said rocker cam to prevent rotation of said retainer socket, a fastener means extending into said rocker cam means and connecting said retainer socket means and said retainer plate through a spherical washer means universally fitted into said socket means, and resilient retainer means connecting said fastener means into prestressed relation with said rocker cam means.
 2. The transducer apparatus of claim 1 wherein said shoe retainer structure is operable independently of said piston barrel means.
 3. The transducer apparatus of claim 1 wherein said fastener means is a threaded bolt extending into said rocker cam and retained by a threaded nut.
 4. The transducer apparatus of claim 3 wherein said resilient retainer means comprises Belleville spring means compressed through said threaded nut.
 5. The transducer apparatus of claim 1 wherein said fastener means and said resilient retainer means are operable to cause said retainer plate to resiliently retain said piston shoes against said slip surface.
 6. The transducer apparatus of claim 4 wherein said fastener means and said resilient retainer means are operable to cause said retainer plate to resiliently retain said piston shoes against said slip surface.
 7. The transducer apparatus of claim 6 wherein said shoe retainer structure is operable independently of said piston barrel means. 